Cruz courts California's Republicans

US presidential candidate Ted Cruz made a plea to the California Republican Party to line up behind him in the state's June primary in his uphill battle to stop frontrunner Donald Trump from grabbing the nomination.

At the same party convention that was the backdrop for chaotic protests against Trump on Friday, Cruz on Saturday (local time) tried to woo party members with support for their long-time issues, like lower taxes and a harder line on immigration.

Former California Governor Pete Wilson gave Cruz his endorsement as he introduced the US senator from Texas.

Cruz received more applause at the convention than either Trump or the third-place candidate, Ohio Governor John Kasich, who also spoke on Friday.

"If we're fractured and we're divided, Hillary Clinton wins and the campaign is lost," he said, referring to the Democratic Party's frontrunner in the November 8 election for the White House.

Now mathematically eliminated from securing the nomination on the first ballot at the party's convention in Cleveland in July, Cruz aims to stop Trump from receiving the 1237 delegates needed to win the nomination outright, forcing a contested convention.

However, the prospect of him being able to do so has grown increasingly slim.

Trump has continued to notch up wins in the nation's nominating contests, including a five-state sweep of the latest string of contests last Tuesday.

Cruz has downplayed the severity of the losses and in his speech on Saturday looked forward to upcoming contests, which he has said will put him on the path to thwarting Trump.

"California is going to decide this Republican primary," he said, referring to the state's June 7 contest.

Trump has been at odds with the party's establishment and has called the system for nominating its candidate "rigged".

Critics say he has played on the fears of his supporters, especially on immigration, by proposing a temporary ban on Muslims entering the country and accusing illegal Mexican immigrants of being rapists and criminals.

On Thursday and Friday, anti-Trump protests erupted outside the candidate's California events. On Friday, he was forced to halt his motorcade and go through a back entrance to a hotel to give a speech to the convention and avoid several hundred loud protesters gathered outside.

Cruz hopes to slow Trump's march toward the nomination in Indiana's primary on Tuesday. The state awards its 57 delegates on a winner-take-all basis by congressional district, possibly granting Cruz a windfall of pledged delegates.

A Real Clear Politics polling aggregation in the state shows Cruz just behind Trump, 35.2 percent to 37.5 percent.

Polls show Cruz has more of a challenge in delegate-rich California, where he lags Trump 28.3 percent to 45.7 percent.